Business Snatches Up Carp

                   Blair Jamieson holds a silver carp which feeds on algae and can weigh upward of 20kg.

Almost 20,000 small grass and silver carp are being sent by a fish breeding business to a start-up land-based aquaculture business in Nelson.

If the venture is successful, Warkworth fish breeders Gray and Blair Jamieson say a new $600,000 aquaculture business could be established at Warkworth.

The first 3000 fish were counted and loaded into tanks for the journey to Gardens of the World at Hope, near Nelson.

While some will be used for clearing weed, about 90 per cent will be grown on, probably for supermarkets. Grass carp are a herbivorous Asian fish species. They have been used to clean waterways since being imported in the 1960s, but have not been bred as a food source in aquaculture, Blair Jamieson says.

They have advantages over carnivorous aquaculture fish stock which are fed large amounts of fish meal and fish oil processed from mainly wild caught fish.

The fish raised by the Jamiesons at New Zealand Waterways Restoration, the only one of its kind in the country, come from fish bred from the original 12 to 15 imports. The Mahurangi Technical Institute at Warkworth was involved in their successful breeding.

Grass carp shouldn't be confused with pest koi carp, Mahurangi Technical Institute director Paul Decker says.

New Zealand conditions are at the bottom end of their survival range and they are considered sterile here in the wild, needing specialist help to breed, says Mr Decker, a partner in the venture.

Grass carp can reach about 18kg. Silver carp, which eat only algae, can weigh slightly more. When grass carp have escaped, as they did in the Waikato River in the 1980s, they failed to breed, Mr Decker says. That's backed by the National Institute of Water and Atmospheric Research.

While many of the Jamiesons' clients are councils, they also undertake clearing of water bodies for private owners. That includes South Head's Lake Kereta which in 2008 was 75 per cent covered in hornwort weed up to 2m high. A recent NIWA report confirms 99.9 per cent of the weed is gone.

Grass and silver carp come under the Conservation Department's permitting system with permits generally costing up to $2000, Blair Jamieson says.

Although there have been instances when permits have been much higher, with permit conditions often prohibitive, he says.

Restrictions are needed, including those to protect native plants which native species like eels feed on, DOC spokeswoman Amy Cameron says.

But the department's concerns about grass carp aren't shared by the Royal Forest and Bird Protection Society.

"We don't have any serious issues with grass carp," Forest and Bird Auckland and Northland officer Nick Beveridge says.

"They don't breed here, nor do silver carp." 

Written by  Delwyn Dickey@Stuff.co.nz